1. Field of the Invention
This invention relates to a substrate treating apparatus and substrate treating method for treating, with a processing or treating liquid, rectangular substrates such as glass substrates for FPD's (flat panel displays), e.g., LCD's (liquid crystal displays) and PDP's (plasma display panels), glass substrates for organic electroluminescence (EL), glass substrates for photomasks, substrates for solar cell panels, substrates for optical disks or printed circuit boards, and the like.
2. Description of the Related Art
A substrate treating apparatus for treating substrates with an etchant is constructed to etch the substrates by supplying the etchant to front surfaces of the substrates while horizontally transporting the substrates supported at back surfaces by transport rollers.
In the conventional substrate treating apparatus which transports a substrate supported at the back surface thereof by transport rollers, the etchant supplied to the substrate will drift around to the back surface of the substrate and seep between the surfaces of the transport rollers and the back surface of the substrates. In such a case, the etchant having seeped between the surfaces of the transport rollers and the back surface of the substrate moves as the substrate is moved by rotation of the transport rollers. This etchant will remain in streaks on the back surface of the substrate.
When this substrate treating step is an etching step for etching silicon oxide film formed on the surface of a glass substrate with fluoric acid, for example, there will arise a problem that the back surface of the substrate is etched by the etchant as the treating liquid remaining in streaks as noted above. Such a phenomenon causes etching unevenness on the back surface of the glass substrate, which makes it impossible to etch both the front and back surfaces of the substrate uniformly. This poses a serious problem particularly when treatment is carried out by moving the substrate back and forth for a fixed period of time by means of transport rollers in a treating chamber.
Japanese Unexamined Patent Publication H7-211684 discloses a substrate cleaning apparatus which immerses a wafer in a tilted state in a cleaning liquid having formed therein ascending currents caused by overflows, and applies megasonic vibration to the cleaning liquid from a lateral direction of the wafer. However, this substrate cleaning apparatus, which is intended to prevent cross contamination of the cleaning tank and the substrate, cannot meet the need to transport and process or treat a large-size substrate.